Pressure vessel closure



March 7, 1967 R. E. LATHAM ETAL 3,307,735

PRESSURE VESSEL CLOSURE Filed NOV. 27, 1964 ATTORNIzY nite Texas Filed Nov. 27, 1964, Ser. No. 414,245 Claims. (Cl. 2Mb- 46) The present invention relates to removable closure means for sealing openings in apparatus utilized to contain hi-gh fluid pressures, and more particularly to a novel, combined closure and seal construction including a double tapered cam device having utility to effect positive making and breaking of a sealed connection between the closure and the fluid pressure confining apparatus.

Apparatus of the general type described herein is disclosed in the commonly assigned Watts Patents Nos. 3,021,974 granted February 20, 1962, and 3,055,537 granted September 25, 1962.

Whereas the just-mentioned patents are primarily directed toward novel sealing element-carrying closures and corresponding high pressure fluid confining element carried seal seats, the present invention is primarily concerned with novel, improved means for effecting sealing engagement and disengagement of a sealing element carrying closure with respect to a high pressure fluid confining element such as a phase change reaction vessel, hydrogenation bomb, petroleum well high pressure casing or the like.

It should be understood that the seal concepts discussed in the specifications of the aforementioned patents, especially No. 3,055,537 are relevant to the apparatus to be discussed herein and therefore are expressly incorporated by reference.

As will become more clearly apparent hereinafter the closure means embodying the principles of the present invention ris adapted to be utilized in any environment where it is desired to effect a sealing engagement and disengagement of a closure with an opening in a high pressure fluid confining element wherein the purpose of the closure is to prevent the leakage of high pressure fluid, confined Within the element, through the opening. The element may be a pressure vessel wherein it is desired to close and seal an open end of the vessel in order to contain a reaction which must take place at high pressure or which involves a sudden, considerable increase or decrease in pressure and then to unseal and open the vessel in order to withdraw reaction products therefrom and the like. The invention also relates to apparatus wherein the pressure confining element is a high pressure conduit, for instance a petroleum casing string wherein the lower end thereof is communicated to pressurized fiuid at extremely lhigh pressures within a mineral formation and it is desired to temporarily close and seal the upper end of the casing. The invention is susceptible of application to fluid pressure confining elements having either large or small openings and cycling pressures and temperatures. As an illustration, the invention disclosed herein is applicable and advantageously usable in effecting a positive sealing engagement and disengagement of a seal carrying closure and vessel having a 16 inch I.D. mouth and a design pressure of 50,000 p.s.i.g. at 100 degrees F.

As is appreciated by those skilled in the art, there are many problems which arise when it is desired to sealingly close a relatively large diameter opening against leakage of pressures of the magnitude just mentioned and as are most frequently encountered in petroleum well and chemical processing equipment environments.

Patent O It has been found that where such extremely high pressures are encountered threaded closure plugs alone are not satisfactory since in most instances the confined pressurized fluid will begin to leak past the threads in a relatively short time. Simila-rly, seals requiring the use o-f plastically deformable gaskets or conventional compressible materials, such as rubber or the like are often not effective in extremely high pressure and/or temperature applications inasmuch as they may deform suiiiciently to allow leakage, especially where sudden pressure changes Within the vessel or conduit are incumbent on the seal. Additionally such seals are also often subject to failure due to the corrosive nature of the `fluid being confined.

Accordingly frusto-conical sealed joints formed by elastically deformable hard metal closure carried sealing elements and corresponding vessel or conduit carried sealing surfaces or seats wherein energy for sealing is stored in the sealing element by elastic deliection thereof, as discussed in the above-mentioned Watts patents and further discussed insofar as the seal concepts are concerned in the specifications of the earlier commonly assigned patents of Watts et al., Nos. 2,766,829, 2,766,- 998 and 2,766,999, all granted October 16, 1956.

In order to obviate certain difiiculties in sealing against high pressures utilizing closures advanced to sealing position and retained there by thread means on the closure and peripherally of the pressure vessel or conduit, various proposals have been made for utilizing non-threaded sealing effecting means such as arcuately movable cams or radially movable Wedges. However such proposals have heretofore not been employable where extremely high fluid lpressures are involved primarily because of the great force needed to bring the closure to a sealed condition with respect to the associated vessel or conduit and which will be sufficient to prevent leakage of pressurized fiuid for long periods of time. Additional considerations in the employment of such high pressure containment arrangements are the extent to which the components are reusable; the extent to which relative movement of the components occurs during pressure fluctuations which may cause galling of relatively moving surfaces which leads to eventual seal leakage and closure failure; and the ease with which a sealed closing of the pressure container can be effected and disengaged.

With regard to this last consideration, it is a special problem in the utilization of pressure containers for working at extremely high pressures, wherein it has been necessary to tightly wedge or cam the closure into sealed condition, to disengage the wedging or camming means so that the closure can be removed.

Accordingly, it is a primary object of the present invention to provide means, in apparatus utilized to contain high fluid pressures, for effecting positive sealing engagement and disengagement of the closure and the fluid pressure confining elements of the apparatus.

A more specific object of the invention is the provision, in apparatus of the type described, of a double tapered cam device usable in a first position thereof to effect a sealing of a closure to the fluid pressure confining element of the apparatus and usable in a second, inverted position thereof to facilitate a disengagement of the closure and the fluid pressure confining element.

Another object of the invention is the provision of fluid pressure confining apparatus comprising a pressure confining element such as a seamless forged thick walled vessel having .a chamber therein opening outwardly through one end of the vessel to define a vessel mouth, means defining an annular groove in the wall of said chamber peripherally of said mouth, the groove having a camming surface constituting a portion thereof; a seal carrying Vessel closure, a plurality of radially movable wedge-like cams received on the outer surface of the closure, and a double tapered cam device having first tapered means thereon for moving said cams radially outwardly into said grooves to force the closure into sealing engagement with the vessel, and second tapered means thereon for moving said cams radially inwardly to positively retract the cams from the grooves to facilitate disengagement of the closure from the vessel.

These and various other objects of the present invention, its principles and the true scope thereof will become more apparent during the course of the following detailed discussion of the structure and operation of a preferred embodiment of the invention, reference being made to the attached drawing wherein the preferred embodiment is shown.

In the drawing:

FIGURE 1 is a top plan view of a pressure vessel incorporating a closure assembly according to the present invention;

FIGURE 2 is a longitudinal sectional view of the vessel and closure assembly taken substantially along line 2-2 of FIGURE 1, the double tapered cam device being sh-own in the wedge expanding position thereof; and

FIGURE 3 is a fragmentary longitudinal sectional view similar to FIGURE 2 but showing the double tapered cam device in the wedge retracting postion thereof.

Referring now to the drawings, a pressure vessel is indicated by the numeral 10. In the embodiment illustrated the vessel lil is generally cylindrical and includes a central chamber 12 which extends centrally and longitudinally within the vessel and opens outwardly through one end 14 of the vessel. The chamber 12, as best been in FIGURE 2 includes a generally cylindrically curved peripheral wall surfacel6 Which merges with a generally hemispherically curved bottom wall surface 18. At the upper regi-on thereof the chamber includes several annular enlargements beginning with a frusto-conical sealing surface 2t) which enlarges as it extends upwardly. The sealing surface 20 terminates in an annular, radially outwardly extending, upwardly facing shoulder 22 which in turn terminates in a larger diameter cylindrically curved surface 24. This latter surface in extending to the end 14 is interrupted by a circumferential groove 26 formed in the vessel side wall 28. As illustrated, the groove 26 comprises a lower upwardly enlarging frusto-conical portion 3f), an upper downwardly enlarging frustoconical portion 32 and a smoothly curved inwardly concave portion 34 connecting the frusto-conical portions 30, 32 and defining the radially outer extent of the groove 26. As can be seen in the embodiment illustrated the curved portion 34 extends considerably lupwardly and radially inwardly from its radially outer extent.

The vessel closure 36 is shown having a generally inverted T-shaped longitudinal cr-oss-section comprised of a lower larger diameter plug portion 38 surmounted by and integrally joined to a smaller diameter tail portion 4t). As shown the plug portion is of a diameter to be slidingly received in the vessel chamber closely adjacent the surface 2d thereof and to be supported at the peripheral region 42 of the lower surface 4d thereof on the upwardly facing shoulder 22. Of course, it is contemplated that the surface 2d could be other than cylindrically curved and the plug portion 38 would then have a corresponding modilied radially outer peripheral shape.

The plug portion 38 further includes means defining a coaxial annular downwardly opening channel 46 in the lower surface thereof. An annular seal ring 48 cornposed of elastic hard metal such as carbon steel or the like is received in the channel d6.

The seal ring 43 is depicted including a generally rectangular sectioned, radially extending annular rib G, from the central region of the lower surface of which an elastically deiiectable lip 52 integrally depends. The lip 52 has a radially outer frusto-conically tapered sealing sur- 4. face 54 thereon arranged to cooperatively, sealingly engage the frusto-conic sealing surface 29 of the vessel.

As disclosed in the hereinbefore mentioned Watts and Watts et al., patents, the sealing surface S4 on the ring 4S is preferably formed so that it extends at a slightly smaller angle with respect to the longitudinal axis of the vessel when unstressed, for instance 2 degrees less, than does the sealing surface 2t? of the vessel. However, because of the elastic nature of the lip 52, the lip and therefore the surface 54, are deflected upon axial movement of the closure to the sealing position thereof shown in FIGURE 2, so that the surface 5d is in stressed sealing engagement with the surface 2t?.

The yoriginal angular difference of the sealing surfaces, their length and the composition of the sealing rin-g are selected according to the principles set forth in the mentioned Watts et al. patents so that the lip 52 will not deflect beyond its elastic limit before axially downward movement of the closure is stopped by the abutting of the seal ring rib lower surface and plug lower surface peripheral region with the upwardly facing shoulder 22.

In the embodiment shown the seal ring 48 further includes a depending lian-ge 56 at the radially inner extent of the rib Sil. The ring 4:8 may conveniently be secured to the closure by a fillet weld S8 between the flange 56 and the lower surface of the closure.

It should be apparent that, whereas a hard metal, elastically deectable lip seal is preferred in the apparatus of the invention because of its demonstrated ability to with* stand extremely high pressure and other harsh environmental conditions without leakage, some other ytypes of seals could be advantageously used with the apparatus of the invention described herein.

The vessel closure 36 is shown having a flat, annular, upwardly facing surface 60 thereon at the upper extent of the plug portion 3S and a flat, .generally circular, upwardly facing surface 62 thereon at the upper extent of the tail portion dll. A plurality of threaded bolt receiving holes 64, eight being shown, are formed in the tail portion so that they are arrayed -in a bolt circle and extend downwardly from the circular flat surface 62 a partial distance into the tail portion 40.

The assembly according to the invention further includes a plurality of complementary, arcuate segmented wedges 66 which together comprise a generally annular structure.

Each arcuate wedge 66 includes a generally radially extending lower surface 68 and a frusto-conically curved radially inner surface 70. The radially outer 4region of each Wedge is defined at least in part by a downwardly diverging frusto-conically curved surface 72 extending from the upper extent of the wedge so as to define an upwardly extending rib 74 between the surface 70 and the surface 72. The surface 72 is shown joined at its lower extent by a second downwardly diverging surface 76 which is shown being Igenerally spherically curved. It is contemplated that the surfaces 32 and 76 may be curved differently from the manner shown in any convenient manner such as by havingy both be frustoconically curved at either the same or at different angles. The lower region of the radially outer part of each wedge 66 includes a generally upwardly diverging frusto-conically curved surface 78 having an arcuate, angularly extending radially outwardly facing groove 30 therein which extends throughout the arcuate extent of each wedge.

An endless retaining spring 82 or equivalent compressive retainer is received in the grooves 8@ and serves to hold the wedges in the segmented annular form shown best in FIGURE l to especially facilitate insertion, removal and transport of the wedges as a group.

An important part of the noval arrangement shown is the double-tapered cam device 84. This member is comprised of a radially extending disk portion 86 from the faces 88, 90 of which integrally extend annular flanges 92 and 94 respectively.

The flange 92 is defined at its inner radial extent by a generally cylindrical surface 96 extending from the disk face 88 and having a diameter of a size such that the fiange 92 surface 96 slidingly engages and is guided for essentially axial movement by, the radially outer peripheral surface of the tail portion of the closure 36. The flange 92 is dened at its outer radial extent by a frustoconical surface 98 which enlarges in radius toward the disk-face 88. The angularity of the surface 98 preferably complements that of the wedge surfaces 70.

Referring to FIGURE 3, the cam device flange 94 is defined at its outer radial extent by a generally cylindrical surface 100 extending from the disk face 90 and having a diameter of a size suchrthat the flange 94 surface 100 slidingly engages and is guided for essentially axial movement by the cylindrical surface 24 of the vessel chamber 12 adjacent the mouth thereof. The flange 94 is defined at its inner radial extent by a frusto-conical surface 102 which decreases in radius toward the disk face 90. The angularity of the surface -2 preferably complements that of the wedge surfaces 72.

A plurality of openings `104 a're formed thruogh the wedge device disk portion 86 in a circular array to axially correspond with the threaded sockets 64.

Centrally of the disk portion 86, an axially directed, threaded screw receiving openin-g 106 is formed. The assembly shown is completed by threaded means 108 shown comprising eight studs having external wrenching nuts 109 thereon, the studs being received in the openings 104 and threaded sockets v64 and threaded means 110 shown comprising a jackscrew received in the threaded opening 106.

The components of the assembly shown are preferablyv composed of durable material such as steel including stainless steel alloys.

By way of example of the type of apparatus with which the present invention is advantageously usable, the assembly depicted can be successfully utilized with a pressure vessel having an outside diameter of 32 inches, a chamber diameter of 16 inches and a chamber mouth diameter of 12 inches wherein the assembly is designed to contain a pressurized uid at 50,000 p.s.i.g. and 100 degrees F. within the chamber. The preferred mode of operation of the apparatus disclosed herein will now be discussed.

To sealingly close the vessel 10, the closure is inserted in the mouth thereof, plug portion downward and lowered until the peripheral portion of the lower surface thereof engages the shoulder 22 and the seal lip sealing surface 54 engages the vessel frusto-conical sealing surface 20'. The group of segmented wedges 66 is lowered through the vessel mouth until the flat lower surfaces 68 of the wedges engage the upper surface of the closure plug portion. Next the double tapered cam device 84 is inserted in the vessel mouth in the orientation thereof shown in FIGURE 2, the flange 92 radially inner cylindrical surface 96 slidingly engages and is guided by the closure tail portion 40 peripheral cylindrical surface and the flange 92 radially outer, frusto-conically curved surface 98 begins to engage the radially inner frusto-conically curved surfaces 70 of the segmented wedges 66. It should be apparent from the structure shown in FIGURE 2 that axial movement of the double tapered cam device 84 effects a radially outward movement of the segmented wedges 66 toward the groove 26. Accordingly, when the eight threaded studs 108 having external wrenching nuts are inserted through the openings 104 and threadably advanced in the sockets 64 the doulble tapered cam device A84 is brought axially toward the closure. As the segmented wedges 66 are forced radially outwardly into the -groove 26, the radially outer surface 76 of the wedges increasingly more forcefully engages the peripheral surface of the groove 26. As can Ibe seen, at the region where the wedges 66 contact the `groove 26 peripheral surface the latter is directed outwardly and downwardly and as shown curves downwardly near its radially outer extent. Due to this arrangement, an increasingly axially directed force becomes applied to the wedge radially outer surfaces 76 as the external wrenching nuts are advanced `downwardly on the studs 108. This force is transmitted through the wedges downwardly on the closure plug portion upper surface and through the plug portion to the vessel shoulder 22 peripherally of the sealing surface 20 thereof.

It should here be noted that because of this arrangement increased downward force on the closure is transmitted to the vessel wall rather than to the deflectable lip seal thus ensuring that the seal will not be overloaded so as to undergo plastic deformation which would destroy its reusefulness or failure which might cause harm to operating personnel and equipment.

To disengage the closure from its sealing relationship with the vessel, the threaded nuts are threadably engaged from studs 108. The jack screw 110 is then rotated to lift the double tapered cam device 84 with respect to the closure and wedges and free it therefrom. The tapered cam device 84 is then inverted and then reinserted in the vessel mouth in the position shown in FIGURE 3 so that the flange 94 radially outer cylindrically curved surface slidingly engages and is guided by the vessel chamber larger diameter cylindrical surface 24 adjacent the vessel mouth and the fiange 94 radially inner frusto-conically curved surface 102 cooperatively engages the upper radially outer frusto-conic wedge surfaces 72 near the upper region of those wedge surfaces. The nuts 109 are threadably reengaged with the studs 108 and utilized to draw the double tapered cam device 84 axially toward the closure. Accordingly, the surface 102 slides along the wedge surfaces 72 forcing the wedges to move radially inwardly, thus relieving the downward force on the closure discussed above.

The jack screw 110 may then be utilized to lift the double tapered cam device 84 away from engagement with the closure and wedges. The vessel 10 may then be opened by lifting out the double tapered cam device 84, then the group of wedges 66 and next the closure 36 itself. Inasmuch as all the parts of the novel apparatus are reusable, a reclosure of the apparatus can easily Ibe effected by repeating the procedures set forth hereinabove.

It should now be apparent that the embodiment of the invention disclosed herein effectively accomplishes each of the inventions objects and clearly illustrates its principles. Inasmuch as the embodiment shown can be modified to some extent without departing from the inventions principles, for instance by modifying the Vessel to include reaction control equipment, or by substituting a conduit for the closed-end vessel shown, all such modifi-V cations should be understood as being within the contemplation of the invention as fall within the spirit and scope of the following claims.

We claim:

1. Apparatus for receiving pressurized fluids comprising a fluid confining element having wall means defining a chamber therein for receiving pressurized iiuid, means defining a chamber mouth at one end of said chamber communicating said chamber with the exterior of said fluid confining element; means defining a closure seat in said chamber; a closure receivable in said chamber abutting said seat to 'block said chamber mouth; cooperative sealing means on said closure and in said chamber adapted to seal the closure with respect to the chamber; means defining a peripherally extending groove in said chamber wall axially toward said chamber and from said closure seat, said groove means including a wedging surface; wedge means received against an outer surface of said closure, said wedge being adapted to be moved between a first position wherein said wedge means bears against said groove wedging surface and forces said closure sealing means to achieve and maintain a sealed condition with respect to the chamfber sealing means and a second position wherein the wedge means is removed from bearing against the groove wedging surface; and a cam device mountable on said closure adjacent said chamber mouth and .having means defining a first camming surface thereon for moving said wedge means from said first position to said second position and a second camming surface thereon for moving said wedge means from said second position to said first position.

2. Apparatus as set forth in claim 1 wherein the groove is annular and the wedge means comprise a plurality of complementary arcuate wedges.

3. Apparatus as set forth in claim 2 wherein each wedge includes means defining an arcuate channel therein; and further comprising an annular compression spring received in said channels to retain said wedges in a segmented annular group.

4. Apparatus as set forth in claim 2 wherein said closure comprises a larger diameter plug portion integrally surmounted by a coaxial, smaller diameter tail portion thereby defining a radially extending shoulder on said plug portion at the juncture thereof with said tail portion; each of said wedges being received on said shoulder.

5. Apparatus as set forth in claim 4 wherein said cam device comprises a disk portion having an annular flange integrally, axially extending from one face thereof and a second annular fiange integrally, axially extending from the opposite face thereof, said first camming surface being located on said first annular flange and said second camming surface being located on said second annular fiange, said cam device being invertable between a first orientation wherein said first camming surface engages said wedges and a second orientation wherein said second camming surface engages said wedges.

6. Apparatus as set forth in claim 5 further including means removably connectable to said closure and engageable with said cam device, said means being operative to draw said cam device axially toward said closure to effect the movement of the wedges between the first and second positions thereof.

7. Apparatus as set forth in claim 6 wherein the removably connectable means comprises threaded members receivable through means defining openings through said cam device and in means defining corresponding threaded sockets in said closure tail portion.

8. Apparatus as set forth in claim 5 additionally cornprising jack means received in said cam device for rnoving said cam device axially away from said closure to facilitate removal of the cam device for inversion thereof.

9. Apparatus as set forth in claim 8 wherein the jack means comprises a jack screw threadably receivable in means defining a threaded opening thr-ough said cam device disk portion and advanceable for abutting engagement with the upper extent of said closure tail portion.

it). Apparatus as set forth in claim 5 additionally comprising means defining a first guide surface on said cam device first annular flange adapted to slidingly engage the peripheral surface of said closure tail portion to guide the cam device for essentially axial movement in its first orientation and means defining a second guide surface on said ca m device second annular flange adapted to slidingly engage the peripheral surface of said chamber adjacent the mouth thereof to guide the cam device for essentially axial movement in its second orientation.

11. Apparatus as set forth in claim 2 wherein said fluid confining element comprises a pressure vessel having a permanently closed end opposite from the chamber mouth end thereof.

12. Apparatus as set forth in claim 2 wherein the cooperative sealing means comprises: means defining a frusto-conical annular sealing surface on said chamber wall adjacent and diverging toward said closure seat, and an annular hard metal sealing ring mounted on said closure, said sealing ring including an integrally depending elastically deflectable lip, and means defining a frustoconical sealing surface on said lip configured for stressed surface to surface sealing engagement with the frustoc-onical annular sealing surface on said chamber wall.

13. In a pressure vessel closure assembly including a vessel having an internal chamber terminating in a chamber mouth, a closure receivable in the chamber mouth against a seat therein to sealingly block the chamber mouth against the escape of fluid pressure from the chamber and radially expansible and contractable wedge means engageable with the closure and vessel to urge the closure toward said seat, the improvement comprising: a cam device for radially expanding and contracting the wedge means, said cam device including a disk, a first annular flange integrally coaxially extending from one face of said disk, means defining a frusto-conical radially outer peripheral surface on said first `annular flange, said radially outer peripheral surface increasing in radius toward said disk, and a second annular flange integrally coaxially extending from the opposite face of said disk, means defining a frusto-conical radially inner peripheral surface on said second `annular flange, said radially inner peripheral surface decreasing in radius toward said disk, said 0am device in a first orientation thereof, with said first flange being presented toward said closure, being adapted to expand the wedge means by engagement thereof by said first fiange peripheral surface and axial movement of said device toward said cl-osure and said cam device in a second orientation thereof, inverted with respect to said first position with said second fiange being presented toward said closure, being adapted to contract the wedge means by engagement thereof by said second flange peripheral surface and axial movement of said device toward said closure.

14. The pressure vessel closure assembly improvement set forth in claim 13 further comprising means removably engageable with the cam device for advancing the cam device axially toward the closure.

15. The pressure vessel closure assembly improvement set forth in claim 14 wherein the cam device includes means defining Ia plurality of axially directed openings therethrough, and the cam device advancing means comprise a plurality of' threaded members received in said openings and having threaded nuts thereon engageable with said closure.

References ited by the Examiner UNITED STATES PATENTS 3,021,974 2/1962 Watts 220-46 3,055,537 '9/1962 Watts 220`46 3,156,375 11/1964 Long 220-46 THERON E. CONDON, Primary Examiner. G, T, HALL, Assistant Examiner. 

1. APPARATUS FOR RECEIVING PRESSURIZED FLUIDS COMPRISING A FLUID CONFINING ELEMENT HAVING WALL MEANS DEFINING A CHAMBER THEREIN FOR RECEIVING PRESSURIZED FLUID, MEANS DEFINING A CHAMBER MOUTH AT ONE END OF SAID CHAMBER COMMUNICATING SAID CHAMBER WITH THE EXTERIOR OF SAID FLUID CONFINING ELEMENT; MEANS DEFINING A CLOSURE SEAT IN SAID CHAMBER; A CLOSURE RECEIVABLE IN SAID CHAMBER ABUTTING SAID SEAT TO BLOCK SAID CHAMBER MOUTH; COOPERATIVE SEALING MEANS ON SAID CLOSURE AND IN SAID CHAMBER ADAPTED TO SEAL THE CLOSURE WITH RESPECT TO THE CHAMBER; MEANS DEFINING A PERIPHERALLY EXTENDING GROOVE IN SAID CHAMBER WALL AXIALLY TOWARD SAID CHAMBER AND FROM SAID CLOSURE SEAT, SAID GROOVE MEANS INCLUDING A WEDGING SURFACE; WEDGE MEANS RECEIVED AGAINST AN OUTER SURFACE OF SAID CLOSURE, SAID WEDGE BEING ADAPTED TO BE MOVED BETWEEN A FIRST POSITION WHEREIN SAID WEDGE MEANS BEARS AGAINST SAID GROOVE WEDGING SURFACE AND FORCES SAID CLOSURE SEALING MEANS TO ACHIEVE AND MAINTAIN A SEALED CONDITION WITH RESPECT TO THE CHAMBER SEALING MEANS AND A SECOND POSITION WHEREIN THE WEDGE MEANS IS REMOVED FROM BEARING AGAINST THE GROOVE WEDGING SURFACE; AND A CAM DEVICE MOUNTABLE ON SAID CLOSURE ADJACENT SAID CHAMBER MOUTH AND HAVING MEANS DEFINING A FIRST CAMMING SURFACE THEREON FOR MOVING SAID WEDGE MEANS FROM SAID FIRST POSITION TO SAID SECOND POSITION AND A SECOND CAMMING SURFACE THEREON FOR MOVING SAID WEDGE MEANS FROM SAID SECOND POSITION TO SAID FIRST POSITION. 